Knitted fabrics, and particularly tubular knitted fabrics, are favored for their comfort, stretchiness and related characteristics resulting from the knitted construction thereof, wherein the fabric is comprised of a series of laterally and longitudinally interconnected loops. Tubular knitted fabric is produced on circular knitting machines, which construct the fabric in continuous lengths. Segments of substantial length are gathered into rolls as they exit the knitting machine and are periodically severed and removed for processing.
Tubular knitted fabric from the knitting machines typically is processed in substantially continuous lengths and can be subjected to various treatments, such as washing, bleaching, dyeing, drying, etc. In many of these operations the fabric is placed under longitudinal tension, frequently while wet. At the end of such processing the fabric typically will have been elongated significantly, and correspondingly narrowed in width because of its interlocking loop construction. It is accordingly necessary to subject the fabric to certain finishing operations, in order to restore the fabric to suitable finished length and width conditions and stabilize its geometry. This enables the fabric to be formed into garments that will not shrink excessively, particularly in the length dimension, when subjected to typical washing and drying operations.
One of the known procedures for stabilizing knitted fabrics is by mechanical compacting in the length direction. An early machine for this purpose, developed in the late 1950s and disclosed in the Cohn et al U.S. Pat. No. 3,015,145, utilizes an opposed pair of cooperating rollers forming a nip. A feed roller is driven at a first surface speed and a retarding roller is driven at a second and slightly slower surface speed. The tubular knitted fabric, in flat, two-layer form, is advanced by the feed roller while being confined against the surface of the feed roller by an arcuately contoured shoe. The confining shoe has a sharply pointed tip positioned slightly (e.g., one-eighth to one-fourth inch) “upstream” from the nip formed by the two rollers. The arrangement is such that the fabric is advanced toward the nip by the feed roller, at the surface speed of the feed roller. When the fabric reaches the nip, it is in simultaneous contact with both rollers and is decelerated by the retarding roller, substantially to the slower surface speed thereof, causing the fabric to be compressively compacted in a lengthwise direction in the small space between the tip of the shoe and the roller nip. Heat and moisture are applied to the fabric during the processing thereof.
The procedure of the Cohn et al '145 patent, while very efficient in compressively shrinking the fabric, has the drawback of acting differentially on the opposite sides of the flat tubular fabric as the fabric passes through the roller nip in simultaneous contact with two rollers operating at different surface speeds at the same point along the fabric length. This gives the tubular fabric a somewhat different appearance on opposite sides. In this connection, the opposite sides of a flat tubular fabric constitute the same (e.g., outside) surface of a garment made from the fabric and any differential surface appearance on different parts of that surface may be readily apparent to the observer.
In an effort to minimize differential surface appearances, the procedure of the Cohn et al U.S. Pat. No. 3,015,146 was developed, which involves passing the flat, tubular knitted fabric through two compacting stations in succession, with the respective stations being reversely oriented with respect to surfaces of the fabric. In this procedure, the fabric is still subjected to simultaneous differential speed roller contact at the respective roller nips. It was hoped that differential treatment at the first station would be offset by an opposite differential treatment at the second station. While this procedure helped, it did not eliminate the problem of differential surface appearance on opposite sides of the fabric. In this process, it was typical for the majority (e.g., 80%) of the total compacting to be imparted to the fabric in the first station, and a much smaller amount to be imparted in the second station. In the above-described process it is also desirable to elongate the fabric slightly between the first and second compacting stages.
A further improvement in equipment and procedures for processing of tubular knitted fabric, developed in the late 1980s, is represented by the Milligan et al U.S. Pat. Nos. 4,882,819 and 5,026,329. In that procedure, there are opposed feeding and retarding rollers driven at different surface speeds, but the rollers are spaced apart a short distance (e.g., one-eighth inch) and do not form a nip. Instead, a pair of opposed, fabric confining blades extend from above and below the two rollers into the narrowest portion of the space between the rollers. The end extremities of the respective blades are opposed and are closely spaced in order to define a narrow confinement zone extending at an angle from one roller to the other. Fabric is driven toward the confinement zone at the surface speed of the feed roller, passes through the confinement zone, and is discharged onto the surface of the retarding roller, operating at a slower surface speed than the feed roller. The fabric is decelerated from the faster speed to the slower speed while being closely confined top and bottom in the confinement zone, and the compacting is imparted to the fabric while the fabric is in that zone. This procedure has a significant advantage over that of the earlier Cohn el al patents in that the fabric is never simultaneously contacted at the same point by the feeding and retarding rollers.